U.S. patent application Ser. No. 360,509, filed on Jun. 2, 1989 and now U.S. Pat. No. 4,932,511, which is assigned to the assignee of the present invention discloses a rotary travel limit stop apparatus for limiting the rotation of a shaft when a predetermined degree of rotation occurs between first and second gears mounted on the shaft. The stopping of rotation is produced by an axially movable stop member which is carried by one of the gears which is displaced into an axial position which engages a fixed stop by rotation of the second gear relative to the first gear. The stop member is carried by a housing which contains the shaft and gears. An annular groove with a variable depth is contained within the second gear which does not carry the stop member. The stop member rides within the annular groove. A compressed spring biases the stop member away from an extended position, which will engage the stop when a predetermined degree of relative rotation occurs between the first and second gears, to a retracted position. When a predetermined degree of angular rotation occurs between the gears which is caused by another gear driving the first and second gears which respectively have a different number of teeth, the stop member is pushed toward the stop by a decrease in depth of the channel as a consequence of the decreased depth of the channel engaging an end of the stop member. The spring is compressed as the stop member is forced outward by the decrease in the depth of the groove.
While the foregoing rotary travel limit stop apparatus is useful in producing stopping of rotation of a shaft when a predetermined degree of relative rotation occurs between gears mounted on the shaft, the spring used for holding the stop member in a retracted position which will not engage the stop member is disadvantageous for certain applications. For example, when the rotary travel limit stop apparatus is utilized in an application for controlling the folding of wingtips into a vertically upward position in aircraft carried by an aircraft carrier, the spring could be subject to breakage. The stop member is not attached to the annular control surface. Breakage of the spring would remove the biasing of the spring in a retracted position which could result in contacting of the stop pin with the stop in an angular position of the shaft which is not desired to prevent stopping in the desired position of the shaft. Furthermore, the annular groove did not provide as high a degree of axial position control as was desired. Buildup in the annular groove, such as hardened grease or grit, could result in inadvertent actuation of the stop mechanism. The support surface in the bore of the gear for the stop pin was shortened as a result of placement of the spring around the stop pin which could result in high stress on both the stop pin and the gear at the surface area where the pin engages the bore.